In the production of polyurethane foams, elastomers, and coatings, a polyol is reacted with a polyisocyanate in the presence of a urethane catalyst. It is well established in the art that physical properties of these foams, elastomers, adhesives, sealants, and coatings can be enhanced by incorporating solids as an organic filler into the polyol side of a polyurethane formulation (i.e., the so-called "B-side") in the form of dispersed polymer particles prior to the urethane-forming reaction. More specifically, it is known that high levels of dispersed polymer are desired since the firmness of the resulting foams and elastomers, generally expressed as load-bearing capacity or modulus, is thereby enhanced. By way of illustration, U.S. Pat. No. 4,454,255 discloses a method of preparing high non-urethane polymer content dispersions in polyols of greater than 30 percent, based on the total polymer plus polyol, employing polyols containing low levels of induced unsaturation to provide polymer/polyols disclosed as having acceptable viscosity.
The incorporation of polymers into the polyisocyanate side (i.e., the so-called "A-side") of a polyurethane formulation is also known. For example, U.S. Pat. No. 4,332,716 discloses a polymer/polyisocyanate dispersion comprising (a) a major amount of a first organic polyisocyanate, (b) a minor amount of a first polymer of at least one ethylenically unsaturated monomer dispersed in said polyisocyanate, and (c) a minor amount of a stabilizer selected from the group consisting of (1) polyoxyalkylene polyols having a number average molecular weight of at least 400 and (2) isocyanato-terminated prepolymer formed by reacting said polyol with a second polyisocyanate. The '716 patent discloses that the polymer/polyisocyanates of that patent have acceptable viscosities in contradistinction to the prior art discussed in that patent.
Another disclosure of polymer/polyisocyanate dispersions having acceptable viscosity is found in U.S. Pat. No. 4,283,500. The '500 patent discloses polymer/polyisocyanates wherein the polymer is formed in situ in the poyyisocyanate by the polymerization of acrylonitrile, alone or together with one or more ethylenically unsaturated monomers, wherein the polyisocyanate comprises at least 2 percent of methylene-bis(4-phenyl isocyanate) (also referred to herein as "MDI") or a polymeric polyisocyanate(s). At column 30, lines 61 through 66 of the '500 patent, it is disclosed that in "Examples F and G in which the polyisocyanate used was composed of large amounts of or all TDI (toluene diisocyanate), the particle sizes of the resulting polymers were relatively large and agglomeration occurred to the extent that the dispersion stability was not considered to be adequate." Such a result is highly undesirable in view of the fact that TDI is the polyisocyanate of choice, particularly when fabricating flexible polyurethanes.
U.S. Pat. No. 4,695,596 discloses polymer/polyisocyanate dispersions suitably having high sllids contents of up to 40 weight percent or higher. Although the physical properties of the polyurethane foams made using the dispersions of the '596 patent are good, further enhancement of these physical properties would be highly desirable, particularly when fabricating foams having a low density of no greater than about 2 pounds per cubic foot from a polymer/polyisocyanate dispersion having a polymer solids content of at least aabout 30 weight percent and a high solids polymer/polyol.
In view of the increasing need in the industry for a higher and higher organic filler solids content in the formulations used to make polyurethane foams, elastomers, adhesives, sealants, and coatings, it would be highly desirable to provide a polymer/polyisocyanate dispersion characterized by advantageous viscosity, even when containing a high non-urethane polymer loading, and also characterized by storage stability against phase separation, particularly in commercially significant polyisocyanates such as toluene diisocyanate; and, furthermore, characterized by advantageous physical properties of the resulting product.